﻿using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Security.Cryptography;
using System.Text;
using System.Text.RegularExpressions;

class Program
{
    static void Main(string[] args)
    {
        var listener = new TcpListener(IPAddress.Loopback, 8080);
        listener.Start();
        while (true)
        {
            using (var client = listener.AcceptTcpClient())
            using (var stream = client.GetStream())
            {
                var headers = new Dictionary<string, string>();
                string line = string.Empty;
                while ((line = ReadLine(stream)) != string.Empty)
                {
                    var tokens = line.Split(new char[] { ':' }, 2);
                    if (!string.IsNullOrWhiteSpace(line) && tokens.Length > 1)
                    {
                        headers[tokens[0]] = tokens[1].Trim();
                    }
                }

                var host = headers["Host"];
                var upgrade = headers["Upgrade"];
                var connection = headers["Connection"];
                var secWebSocketKey = headers["Sec-WebSocket-Key"];
                var secWebSocketOrigin = headers["Sec-WebSocket-Origin"];
                var secWebSocketProtocol = headers["Sec-WebSocket-Protocol"];
                var secWebSocketVersion = headers["Sec-WebSocket-Version"];

                /*var key = new byte[8];
                stream.Read(key, 0, key.Length);

                var key1 = headers["Sec-WebSocket-Key1"];
                var key2 = headers["Sec-WebSocket-Key2"];

                var numbersKey1 = Convert.ToInt64(string.Join(null, Regex.Split(key1, "[^\\d]")));
                var numbersKey2 = Convert.ToInt64(string.Join(null, Regex.Split(key2, "[^\\d]")));
                var numberSpaces1 = CountSpaces(key1);
                var numberSpaces2 = CountSpaces(key2);

                var part1 = (int)(numbersKey1 / numberSpaces1);
                var part2 = (int)(numbersKey2 / numberSpaces2);

                var result = new List<byte>();
                result.AddRange(GetBigEndianBytes(part1));
                result.AddRange(GetBigEndianBytes(part2));
                result.AddRange(key);
                */

                /*var response =
                    "HTTP/1.1 101 WebSocket Protocol Handshake" + Environment.NewLine +
                    "Upgrade: WebSocket" + Environment.NewLine +
                    "Connection: Upgrade" + Environment.NewLine +
                    "Sec-WebSocket-Origin: " + headers["Origin"] + Environment.NewLine +
                    "Sec-WebSocket-Location: ws://localhost:8080/websession" + Environment.NewLine +
                    Environment.NewLine;*/
                
                var response =
                    "HTTP/1.1 101 Switching Protocols" + Environment.NewLine +
                    "Upgrade: WebSocket" + Environment.NewLine +
                    "Connection: Upgrade" + Environment.NewLine +
                    "Sec-WebSocket-Accept: " + headers["Origin"] + Environment.NewLine +
                    "Sec-WebSocket-Location: ws://localhost:8080/websession" + Environment.NewLine +
                    Environment.NewLine;

                var bufferedResponse = Encoding.UTF8.GetBytes(response);
                /*stream.Write(bufferedResponse, 0, bufferedResponse.Length);
                using (var md5 = MD5.Create())
                {
                    var handshake = md5.ComputeHash(result.ToArray());
                    stream.Write(handshake, 0, handshake.Length);
                }*/
            }
        }
    }

    static int CountSpaces(string key)
    {
        return key.Length - key.Replace(" ", string.Empty).Length;
    }

    static string ReadLine(Stream stream)
    {
        var sb = new StringBuilder();
        var buffer = new List<byte>();
        while (true)
        {
            buffer.Add((byte)stream.ReadByte());
            var line = Encoding.ASCII.GetString(buffer.ToArray());
            if (line.EndsWith(Environment.NewLine))
            {
                return line.Substring(0, line.Length - 2);
            }
        }
    }

    static byte[] GetBigEndianBytes(int value)
    {
        var bytes = 4;
        var buffer = new byte[bytes];
        int num = bytes - 1;
        for (int i = 0; i < bytes; i++)
        {
            buffer[num - i] = (byte)(value & 0xffL);
            value = value >> 8;
        }
        return buffer;
    }
}